That was Karsoth, the usurper Chamberlain. Not really a good example, since pretty much everything he did was just yet another excuse from :tonyg: for him to be twirling a moustache, or for the reader to not like him. It was designed to make people mad, and the parallel between that and the ongoing scandals within the Church irl that aided in that design was pretty blatant.
There is only one other mention of homosexuality in Amarr PF (ignoring the drug-fuelled spacelesbian orgies of Jamyl in T1, also a :tonyg: thing) was in a chronicle, and while it was confirmed by the author that a character in the chronicle happened to be gay, it was never, ever made clear whether it was that he was gay that made his interest an issue, or whether it was simply that he was a priest and the object of his intended affections was a slave.
To date, the Caldari State is the only entity where any sort of taboo is explicitly stated as being present. Since it's a pretty big issue, the lack of mention implies to me that it isn't taboo in the Empire, Kingdom or Mandate. What I would imagine to be taboo, or at least considered inappropriate, is (excessive) public displays of affection regardless of who's involved or their genders. You want to hold hands in public while out on a date, probably not an issue. Just don't start making out in the town square.